LF: Field Strength Meter

[CHRISTOPHER OSBORN <c.cjo@btinternet.com>]

Has anyone built the field strength meter from the 'LF Experimenter's Handbook' (p 83) ?
I intend to make a similar one but for the 500 kHz band, however a couple of things in the artical are confusing me:
(1)
The formula (3) for a Helmholtz coil pair gives  H = I / (1.40 * r )
where I is the coils' current in Amperes and r the coils'  radii in metres.
Looking on the internet the Helmholtz formula also includes the permeablility of free space  -  4 * PI * 10 ^ -7  !!    so is there a misprint ?
(2)
The artical gives the required magnetic field to equate to an electric field strength of  5 mV / m as being 13.3 uA / m
I follow the working for this ok but if the Helmholtz coils are being fed from a signal generator with a series 50 ohms resistor surely the output voltage setting would be impracticably low  -  about  540 uV ( I think )

I can make the Helmholtz coils as per the artical
 (i.e. with radii of 0.292 m) so what signal generator setting would I need to generate the required field strength of 13.3 uA / m and how would I achieve this ?
Any lessons learned by members of LF Group while making this meter would be much appreciated.

73 Chris G3XIZ

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